Gastrointestinal disturbances are the most frequent adverse effect of Azithromycin but are usually mild and less frequent than with erythromycin. Headache, somnolence and taste disturbances may occur. Severe hypersensitivity reactions occur rarely but may be prolonged. Thrombocytopenia and mild transient neutropenia have been rarely reported in patients receiving Azithromycin. Pain and inflammation may occur at the site of intravenous infusion particularly at high concentration.